Tree species richness and phytomass carbon stock along the urban-rural gradient in trees outside forests of Kathmandu valley, Nepal

Abstract

ABSTRACT Trees outside forests (TOF) are woody plants found on land which is less than 0.5 ha. These are important for biodiversity conservation and carbon storage. This study was conducted in Kathmandu Valley, central Nepal to determine tree species diversity and phytomass carbon stock patterns along the urban to rural spatial gradient of TOF. A detailed inventory was conducted across a total of 209 randomly selected points generated by MS Excel using circular plots of 20 m radius each. A total of 6,210 trees from 150 species belonging to 111 genera and 57 families were recorded under three strata (urban, suburban and rural). Out of 150 species, 53.33% were native and 46.67% were exotic. The average tree density was found to be higher in the suburban stratum (248.44 ha−1) compared to the urban (232.58 ha−1) and the rural (224.88 ha−1) strata. Species richness was found to be higher in the rural stratum (14.09 ha−1) compared to the urban (9.85 ha−1) and the suburban (9.70 ha−1) strata. But average species richness was found to be highest in the urban stratum (55.95 ha−1) followed by the suburban (46.31 ha−1) and the rural (45.74 ha−1) strata, respectively. Similarly, the average phytomass carbon stock recorded was highest in the urban stratum (39.41 t ha−1) compared to the rural (29.19 t ha−1) and the suburban (26.06 t ha−1) strata. The average phytomass carbon stock varied significantly between the native and the exotic species only in the urban stratum but not in the suburban and the rural strata. This study provides baseline data useful for green urban planning and development as well as carbon sink management.